问题通过Segue将数据传递给不同的View Controller

Question

我试图将一个对象从一个视图控制器传递到另一个视图控制器，并且在调用下一个视图控制器时该对象似乎是空的。我发现其他论坛建议我使用类似的东西来传递我的User对象。

var user: User!
override func viewDidLoad() {
        super.viewDidLoad()

        oauthswift = OAuth1Swift(
            consumerKey:    CONSUMER_KEY,
            consumerSecret: CONSUMER_SECRET,
            requestTokenUrl: "https://api.twitter.com/oauth/request_token",
            authorizeUrl:    "https://api.twitter.com/oauth/authorize",
            accessTokenUrl:  "https://api.twitter.com/oauth/access_token"
        )
        handle = oauthswift.authorize(
            withCallbackURL: URL(string: "oauth-swift://oauth-callback/twitter")!,
            success: { credential, response, parameters in
                print("OAuthToken: \(credential.oauthToken)")
                print("OAuthSecret: \(credential.oauthTokenSecret)")
                print("User ID: \(parameters["user_id"]!)")
                self.user = User(oauthswift: self.oauthswift, consumerKey: CONSUMER_KEY, consumerSecret: CONSUMER_SECRET, oAuthToken: credential.oauthToken, oAuthSecret: credential.oauthTokenSecret)
                func prepare(for segue: UIStoryboardSegue, sender: Any?) {
                    if let feedViewController = segue.destination as? FeedViewController {
                        feedViewController.user = self.user
                    }
                }
                self.performSegue(withIdentifier: "goToFeed", sender: self)
                // Do your request
        },
            failure: { error in
                print(error.localizedDescription)
                print(self.handle)
        }
        )

        // Do any additional setup after loading the view, typically from a nib.
    }

执行goToFeed时，User对象为空。我正在闭包中执行初始化，所以在我看来用户应该完全填充。我假设我使用segue函数的方式不正确？任何想法都表示赞赏。

Answer 1

你误解了如何使用prepare(for:)。它必须是顶级实例方法，而不是嵌套函数。调用performSegue(withIdentifier:)后会调用它：

var user: User!

func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let feedViewController = segue.destination as? FeedViewController {
      feedViewController.user = self.user
    }
}

override func viewDidLoad() {
        super.viewDidLoad()

        oauthswift = OAuth1Swift(
            consumerKey:    CONSUMER_KEY,
            consumerSecret: CONSUMER_SECRET,
            requestTokenUrl: "https://api.twitter.com/oauth/request_token",
            authorizeUrl:    "https://api.twitter.com/oauth/authorize",
            accessTokenUrl:  "https://api.twitter.com/oauth/access_token"
        )
        handle = oauthswift.authorize(
            withCallbackURL: URL(string: "oauth-swift://oauth-callback/twitter")!,
            success: { credential, response, parameters in
                print("OAuthToken: \(credential.oauthToken)")
                print("OAuthSecret: \(credential.oauthTokenSecret)")
                print("User ID: \(parameters["user_id"]!)")
                self.user = User(oauthswift: self.oauthswift, consumerKey: CONSUMER_KEY, consumerSecret: CONSUMER_SECRET, oAuthToken: credential.oauthToken, oAuthSecret: credential.oauthTokenSecret)
                self.performSegue(withIdentifier: "goToFeed", sender: self)
                // Do your request
        },
            failure: { error in
                print(error.localizedDescription)
                print(self.handle)
        }
        )

        // Do any additional setup after loading the view, typically from a nib.
    }